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A novel hybrid integration strategy for compact, broadband, and highly efficient millimeter-wave (mmWave) on-chip antennas is demonstrated by realizing a hybrid on-chip antenna, operating in the [27.5–29.5] GHz band. A cavity-backed stacked patch antenna is implemented on a 600 $\mu$ m thick silicon substrate by using air-filled substrate-integrated-waveguide technology. A hybrid on-chip approach is adopted in which the antenna feed and an air-filled cavity are integrated on-chip, and the stacked patch configuration is implemented on a high-frequency printed circuit board (PCB) laminate that supports the chip. A prototype of the hybrid on-chip antenna is validated, demonstrating an impedance bandwidth of 3.7 GHz. In free-space conditions, a boresight gain of 7.3 dBi and a front-to-back ratio of 20.3 dB at 28.5 GHz are achieved. Moreover, the antenna is fabricated using standard silicon fabrication techniques and features a total antenna efficiency above 90% in the targeted frequency band of operation. The high performance, in combination with the compact antenna footprint of $\text{0.49}\,\lambda _{\rm min} \times \text{0.49}\,\lambda _{\rm min}$ , makes it an ideal building block to construct broadband antenna arrays with a broad steering range. [ABSTRACT FROM AUTHOR]

A novel wideband substrate integrated waveguide (SIW) antenna topology, consisting of coupled half-mode and quarter-mode SIW resonant cavities, is proposed for operation in the 60 GHz band. This innovative topology combines a considerable bandwidth enhancement and a low form factor with compatibility with low-cost printed circuit board manufacturing processes, making it excellently suited for the next generation, high data rate wireless applications. Moreover, exploiting SIW technology, a high antenna-platform isolation is obtained, enabling dense integration with active electronics without harmful coupling. The computer-aided design process yields an antenna that covers the entire 57-64 GHz IEEE 802.11ad band with a measured fractional impedance bandwidth of 11.7% (7 GHz). The measured maximum gain and radiation efficiency of the prototype are larger than 5.1 dBi and 65%, respectively, within the entire impedance bandwidth. [ABSTRACT FROM PUBLISHER]

Commonly used connection methods for measuring antennas in the mm-wave range, like connectors or probes, influence the intrinsic behavior of the antenna under test (AUT). It is shown that nearby structures supporting the antenna and probe or connector cause strong interference on the measured antenna pattern. A new connection setup is proposed eliminating the interfering signal. This is confirmed by a detailed simulation model and verified with experimental results. Furthermore, the probe radiates significantly due to the discontinuity from the transitions of the probe tip to the microstrip line. This radiation influences the signal-to-noise ratio, i.e., the dynamic range. Measures are proposed to reduce this interference, resulting in an improved signal-to-noise ratio by approximately 15 dB. [ABSTRACT FROM PUBLISHER]

The spatial filtering in an orthogonal frequency division multiplexing (OFDM) radio-over-fiber network is proposed to boost its capacity using broadband optical true time delay enabled microwave beam steering. The observed suppression ratio of the spatial filtering is 19.4 dB. The optical delivery and directional wireless transmission of 3.975 Gb/s OFDM data on a 19-GHz microwave carrier is studied. The observed beam directing-induced bit error ratio improvement is more than four orders of magnitude. [ABSTRACT FROM PUBLISHER]

This article describes the possible factors that can introduce discrepancies between measurements and three-dimensional EM simulations of millimeter-wave (mm-wave) antennas. The effects of the choice of the simulation solver, the relative permittivity and the homogeneity of the substrate material, the manufacturing tolerance, and the measurement errors are discussed. It is concluded that a fair comparison between measurements and simulations of mm-wave antennas can only be made if all these possible causes of discrepancies are taken into account. [ABSTRACT FROM AUTHOR]

It is shown that metal gratings can be used to improve the cross polarization of circularly-polarized aperture-coupled microstrip antennas. The metal gratings reduce edge diffraction from the finite-size grounded dielectric slab on which the antennas are printed. The edge diffraction is due to surface waves that can propagate in the grounded dielectric slab. The design of the metal grating is based on an analytical model, which results in a first-order estimation for the design of the metal grating structure. The model provides physical insight and appears to be accurate enough for the application. Using this model, a prototype was developed, consisting of a circularly-polarized 2 x 2 microstrip array with associated feeding network. Measurements show that the axial ratio can be reduced down to 1.75 dB within the beam width of the antenna. [ABSTRACT FROM AUTHOR]